Image processing system

ABSTRACT

An image processing system integrates the scanning function with image processing function. The scanned image can be directly transmitted to a printer for high quality reproduction to serve a “scan to print” function. The system can also transmit the scanned image with or without being processed to a computer for further processing. The output from the computer can be transformed into image for rapid printout.

[0001] This application is a division of patent application Ser. No.08/595,028 filed Jan. 31, 1996.

FIELD OF THE INVENTION

[0002] This invention relates to an image processing system for digitalprinter in conjunction with a scanner or document reader to serve as acopier.

BACKGROUND OF THE INVENTION

[0003] Due to the popularity of office automation, it is common practiceto equip an office or home with a scanner and a printer as shown inFIG. 1. (Note that the word “scanner” may also be termed as “imagereader”, “image inputting device” or “document reader”.) On the otherhand, a digital copier is a bulky and expensive piece of equipment. Itis desirable to reduce the number of equipment in an office or home toeconomize on space, expense and energy consumption.

[0004] A digital copier is actually a combination of a scanning device,a printing device and an image processor. As shown in FIG. 2, a digitalcopier consists of a scanning unit 101, a system control unit 102, animage processing unit 103, a printing unit 104 and an operation panel105. Generally, the scanning unit 101 uses a charge coupled device (CCD)image sensor or contact image sensor (CIS) to scan the images of adocument for each narrow region, i.e. on a pixel basis, to produce ananalog image signal. The analog signal is quantized and converted intodigital signals. After various kinds of signal processing in the imageprocessing unit 103, the digital signal is applied to the printing unit104 to reproduce the document images. The operation panel 105 is used toselect various image processing methods and copy count.

[0005] The advantages of such a digital copier is having imagemanipulation capability and better printout quality compared withconventional low-end and mid-end copier. The drawback is its expense andbulkiness.

[0006] It can be seen that the function of a digital copier is redundantwith that of a scanner and a printer. The processing and programming ofa digital copier is similar to that of a scanner plus an imageprocessing system and a printer.

[0007] At present, a printer is customarily used in connection with apersonal computer. Data are transferred through an interface driver,such as the Centronics Interface. Due to the limitation of transmissionspeed and image processing of huge amount of data, it is not possible toincrease the printing speed. Without any special image processingdevice, or real time image processing system or algorithm, the printeris incapable of achieving high quality and high speed printing.

[0008] According to a conventional method of binarized gradationprocessing an image by way of dither, the image signal read is directlycompared as an analog signal with a dither threshold value or after ithas been converted to the digital signal. This digital signal iscompared with the dither threshold value and in this case, the ditherthreshold value is two-dimensionally changed in correspondence to thedivision of the read image.

[0009] However, an image processed with the dither method results inpoor resolution with sawtooth edge in text and with Moire pattern.

SUMMARY OF THE INVENTION

[0010] The objects of this invention are to combine the functions of ascanner, a computer and a printer and to effect the followingprovisions:

[0011] 1. A provision to store the scanned image input in the imageprocessor, and to output directly the stored image rapidly to theprinter;

[0012] 2. A provision to translate the stored image and then to outputthe stored image rapidly to the printer;

[0013] 3. A provision to output the stored image to a computer forstorage;

[0014] 4. A provision to translate the stored image and then to outputthe translated image to a computer;

[0015] 5. A provision to output the scanned image input directly to acomputer without image processing;

[0016] 6. A provision to view the stored image in the computer and tooutput rapidly to the printer;

[0017] 7. A provision to view or to edit the stored image, to view againafter image processing, and then to output rapidly to the printer;

[0018] 8. A provision to first transform the information in the computerinto image, and then to output the information rapidly to the printer;

[0019] 9. A provision to connect a video interface with a printer tofully utilize the high speed capability of the printer.

[0020] These objects are achieved by integrating the scanning functionand the image processing function as an “image processing system”. Thescanned image can be directly transmitted to a printing device for highquality reproduction serving a “scan to print” function. This inventioncan also transmit the scanned image with or without processing to acomputer for further processing. The output from the computer istransformed into image information for rapid printout.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 shows a conventional office computer setup including ascanner and a printer.

[0022]FIG. 2 shows the block diagram of a conventional setup of adigital copier.

[0023]FIG. 3 shows the basic system of the present invention, combiningscanning and image processing, and outputting to a printing setup tofunction as a digital copier.

[0024]FIG. 4 shows the block diagram to transmit the scanned image to acomputer through a computer interface. Alternatively, the scanned image,after image processing, can be transmitted to the computer.

[0025]FIG. 5 shows a block diagram for a computer interface to transmitprinting information to the printing device through the image processorwith or without being processed by the image processor.

[0026]FIG. 6 shows the block diagram of the present invention.

[0027]FIG. 7 shows the construction of the image processor.

[0028]FIG. 8 shows a 3×3 window to detect the existence of an edge.

[0029]FIG. 9 shows an error diffusion algorithm.

[0030]FIG. 10 shows the flow diagram for automatic background detection.

[0031]FIG. 11A shows the connection of the present invention to theprinting device through a video interface; FIG. 11A shows the connectionof the present invention to the printing device through a parallel port;FIG. 11C shows the connection of the present invention to the printingdevice through a universal serial port.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0032] This invention comprises the following features:

[0033] a scanning equipment to furnish scanning input data;

[0034] an interface connected to a printer;

[0035] a controller, which controls, processes and outputs gray andcolor information from the scanner to the printing device, andsynchronizes the input image with the output image for minimizing therequired storage capacity;

[0036] a clock generator to generate clock pulse and control timing forthe image processing system;

[0037] an operating panel to manipulate input keys;

[0038] an indicating device to indicate operation or current status,printing selection, print density, etc.

[0039] Also included in the system is a provision to implement the“error diffusion method” for overcoming the drawback of the “dithermethod”. Image correction, edge emphasis, “decision making method”, etc.are used to improve the quality of the image printout.

[0040] Referring to FIG. 3, this invention integrates the scanning andimage processing functions and outputs to the printing device to effectdigital printout. The complete system includes: a scanning device 305,an image processing device 301, an operation panel 304, a printinginterface 306 and a printing device 303.

[0041] When a colored or black-and-white document is scanned by thescanner 305, there are many levels of image signals. These multiplelevel signals are processed by an image processor 301 or by an“Application Specific Integrated Circuit, ASIC”. According to the user'sselection through the operating panel, gray level image information canbe produced.

[0042] The signal from the scanning device 305 is fed to the imageprocessor 301, which obtains the user's chosen information fromoperation panel 304 for the selection of processing mode and thequantity number of copies, and combines with the output from the scanner305. The combined signal is processed in the image processor, and fed toa printer or printing Device (such as a printing engine) 303 via a videoprinting interface 306. The printing unit 303 modulates the receivedvideo image signal into laser beam and reproduces the image.

[0043] Referring to FIG. 4, through the computer interface 310, thescanned image can be transmitted to the computer 308 without passingthrough the image processor 301. The scanned image can also elect to gothrough the image processor 301 before transmitting to the computer 308.Whenever the computer outputs any information, the information isconverted into image signal through the image processor 301.

[0044] Referring to FIG. 5, the printing information is transmitted tothe printer 303 through the computer interface 310 and the imageprocessor 301.

[0045]FIG. 6 shows the block diagram 601 of the system. The scannedinformation from the scanning device 602 is controlled by a centralprocessing unit 602. The image processor 603 processes the scannedinformation while in an Image Processing Mode according to the selectionof the operation panel 611. An image storage device 605 stores theprocessed and pre-processed information. The interface 607 is connectedto a printer or printer engine through a video interface according tohandshaking command and status, synchronization signals such as PageSynchronization, and Line Synchronization synchronize with the videodata for printout. An operation panel 611 includes a Display 614 fordisplay of magnification/reduction ratio and page number, LED 613 fordisplay of operating mode and printer status, etc. The key pad 612inputs the operating mode, the magnification/reduction ratio, pagenumber, etc. A central processing unit 604 constitutes the controlcenter, through which the printing interface 607 handshakes with theexternal printer, and the operation panel 611 displays the status. Theimage processor 603 controls the synchronization and operation of thescanning, processing and printing steps.

[0046] In the scanning unit, the original document is placed on a glassplaten. An image is projected or a sheet of original image is scanned bymeans of an exposure lamp, a lens and an image sensor capable of readinga line image (e.g. a CCD sensor).

[0047] Various kinds of image processing information are read by thescanning device as controlled by a controller. The computer interfacemay be a SCSI (Small Computer System Interface) interface, parallelinterface, etc. The resolution of the scanning unit is e.g. 300 dots perinch in the main scanning direction and a variable resolution in thesub-scanning direction, e.g. ranging from 75 lines per inch through 600lines per inch.

[0048] Referring to FIG. 6, the image processing system 601 consists ofa scanning device 602, an image processing unit 603, a printinginterface 607, a central processing unit (CPU) 604, an operation panel611, a program storage memory 609, a working memory 608 for the CPU, andan image memory 605.

[0049] The central processing unit 604 controls the scanning area, thescanning mode, and the scanning speed of the scanner. When the imagesignal is transmitted to the image processor, the image processorproceeds to process the signal according to the instruction of thecontrol panel 611. The processed image as controlled by the imageprocessing unit 603 can control the feeding speed of the scanned image,the synchronization with the printer, or selecting to transmit theprocessed signal to the computer through the computer interface 615.

[0050] The control and synchronization of the entire system includingthe scanner, the image processor 603 and external printer . . . etc. arecontrolled by the central processing unit 604. The control modes, thetable of contents and mathematical formulas are stored in an EPROM ormasked ROM 609. The control panel 611 contains different input keys 612for user to select the necessary modes, indicator 614 and light emittingdiodes 613 to display the operating modes of the printer and operationof the program. The indicator 614 has many display areas and can bedisplayed with liquid crystal or similar displays. The display candisplay the input numbers as keyed on the operating panel's imageprocessing mode and density control, or can display the reproducednumerical information. The light emitting diode 613 indicates thecurrent states and conditions of the system. The processed image can betransmitted to the computer or transmitted to the printer for output.The image scanned by the scanner 602 can be sent to the computer. Thematerial to be printed can be sent to the printer directly with orwithout being processed by the image processor 603.

[0051] Referring to FIG. 7, a typical construction of the imageprocessor 701, corresponding to the block 603 in FIG. 6, adapted toprocess inputting multiple image signal from external scanning unit andoutputting processed video image signal to external printing unit. Asshown in FIG. 7, the scaling unit 702 under the control of external CPUenlarges or reduces the size of images of the respective sizes oforiginals with reference to the size of a record sheet so that theimages of the originals can be accommodated in the recording areas ofthe sheet. The image data processed in the scaling unit are stored inthe storage memory means through memory control and interface unit 710and can be retrieved from storage memory means for image processing nextline.

[0052] Referring to FIG. 7, a background detection and density controlunit 703 is provided for automatically detecting the density of documentbackground so as to provide a background threshold for image processing.To achieve the dynamic background detection, according to the presentinvention, it is to provide a digital peak hold circuit which holds thepeak threshold in a count-up/down counter. The counter counts up whenthe input image signal is greater than the peak threshold, and countsdown when the consecutive eight input image signals is lower than thepeak threshold. The peak threshold may be either a fixed backgroundthreshold selected from operation panel or the dynamic backgroundthreshold generated from the digital peak hold circuit. The finalbackground threshold is determined in accordance with the selection ofdensity control level and the peak threshold value.

[0053] Referring to FIG. 7, an image correction unit 705 is provided toadjust the input scanning gamma curve to output printing gamma curve, soas to obtain the best printing quality and result. The image correctioncurve can be changed by the information from the operation panel.

[0054] Referring to FIG. 7, an edge detection unit 704 is provided toadopt a 3×3 window to detect the existence of an edge. An edge thresholdis assigned by the information from the operation panel to detect if anedge which is currently covered by the 3×3 window exists. If an edge ispresent, the edge detected signal is generated to the “binary outputdecision making unit” for further image processing. A detaileddiscussion of this separation will be given below.

[0055] Referring to FIG. 7, the address generator unit 709 and memorycontrol & interface unit 710, are provided for external storage memoryaccess. The address generator unit 709 generates the image correctionaddress, 3×3 window address, CPU address, and error diffusion address.The addresses are multiplexed to provide a specified address inspecified memory phase. The image processor handles different processand fetches or stores specified data from specified memory address indifferent memory phases.

[0056] Referring to FIG. 7, an error diffusion unit 706 is provided toperform “halftone image processing”, so that a user can select eitherthe error diffusion or dither method to process the image.

[0057] If the error diffusion method is selected, the image signal fromthe scanning device 602 is fed to the scaling unit 702 and the densitycontrol unit 703, which are then combined with the output from the imagecorrection unit 705, edge detection unit 704 and error diffusion unitand fed simultaneously to the binary output decision making unit 707 toobtain the error diffusion effect. If the dither method is selected, theerror diffusion unit 706 only furnishes the “dither table” and does nothave the error diffusion function. Then the binary output decisionmaking unit 707 outputs a dithered image.

[0058] The advantages of the error diffusion method are that theresolution is maintained in its best condition and is free from unwantedtextures. There are some disadvantages using error diffusion method,such as: white background is disturbed by snake-like noise, the printedimage is too dark to distinguish the details, and the printed textexhibits a coarse edge. In order to improve the above disadvantages,binary output decision making unit is introduced to remove backgroundsnake-like noise, and enhance the edge of the text. An overly darkprinting image is improved by an image correction curve.

[0059] Different combinations of coefficients can produce printingeffects. These coefficients include those for: background and densitycontrol unit 703, edge detection and intensifying unit 704, and imagecorrection unit 705. An I/O interface unit 711 between the centralprocessing unit CPU and the output/input serves as the interface for thecentral processing unit and the interface for the temporary storage ofoutput/input. A time sequence and control unit 712 provides the clockpulses and controls the timing signals. The basic clock is supplied froman external crystal or oscillator. The clock and control generator 712supplies not only the timing clocks and the control signals for thedifferent internal units, but also output timing pulses for the entiresystem.

[0060] Referring to FIG. 8, the 3*3 window is constructed with thecurrent-processing pixel P21, as the central entity and the eightadjacent pixels P10, P11, P12, P20, P22, P30, P31, P32 surrounding thecentral pixel P21, as the neighborhood entities.

[0061] The absolute difference between the gray levels of the centralpixel and one of the neighborhood pixels, which is greater than the edgethreshold, indicates that an edge exists between the central pixels andone of the adjacent pixels.

[0062] The error diffusion algorithm is shown in FIG. 9. The error iscalculated by the original image signal A[i, j] subtracts the videoimage data B[i, j] which is determined by the binary output decisionmaking unit 707, which distributes the error by multiplying a factor of{fraction (7/16)}, {fraction (3/16)}, {fraction (5/16)}, {fraction(1/16)} respectively to the surrounding pixels of Pa, Pb, Pc, Pd.

[0063] Referring to FIG. 10, automatic background detection is based onusing the peak value of certain area as a dynamic reference value. Thisvalue is transmitted to the decision making unit for further treatmentto subtract from the picture content, so that the details in thebackground area can be read.

[0064]FIG. 11A shows the connection of the printing device to thepresent invention through a “video interface”.

[0065]FIG. 11B shows the connection of the printing device to thepresent invention through a “parallel port”.

[0066]FIG. 11C shows the connection of the printing device to thepresent invention through a “universal serial bus”.

[0067] n summary, a scanning device can be connected to an externalprinting device through this invention to achieve high speed, highquality printout. This invention solves not only the problem of slowspeed, poor quality of conventional copier, but also the problem of highequipment cost, high maintenance cost, large space and high energyconsumption.

[0068] Another feature of the present invention is the transformation ofoutput information into image information which is then transferred tothe printer for printout. This feature solves the problem of inferiorand slow output quality of the computer output.

[0069] The foregoing description merely discloses the preferredembodiment as an example. This invention is by no means limited to thisembodiment. Any equivalent techniques to achieve the same results areall within the scope of this invention.

What is claimed is:
 1. An image processing system to receive and processscanned information from a scanner, comprising: a central processingunit to control the scanning of said scanner and the transmission ofsaid scanned information; an image processor to process said scannedinformation according to a user-selected printer; an image storagedevice connected to said image processor to store any processed imageinformation, wherein said processed image information can be sent to theuser-selected printer for printout.
 2. An image processing system asdescribed in claim 1, further comprising a means for letting a userselect the user-selected printer.